In this paper, the challenging points regarding the high temperature physical chemistry of slags to
achieve the improved and stable electric arc furnace (EAF) or electric smelting furnace (ESF)
technology on the way to green steel will be reviewed, and the recent experimental and modelling
research will be discussed. For example, the initial melting phenomena of hot briquetted iron (HBI)
and the slag formation behaviour was observed using a high-frequency induction furnace. Main
component of gangue oxides in HBI was SiO2, Al2O3, and CaO in conjunction with unreduced iron
oxide. To increase the dephosphorisation efficiency, the distribution ratio of phosphorus between
metal and slag was calculated using FactSage™ software, version 8.2 (CRCT ThermFact, Inc.,
Montreal, Canada) and was compared to the measured results. The optimisation of slag chemistry
is required not only for maximum dephosphorisation efficiency with good slag foamability but also
for minimum slag volume with less refractory corrosion in EAF process. The slag chemistry is also
one of key parameters affecting the operation efficiency in ESF in view of FeO reduction behaviour,
viscosity, sulfide capacity, etc.